The invention relates to chucks and, more particularly, to a chuck on which is mounted a cardboard core or tube on which a web, such as plastic film, is spirally wound after the web has been slit into an appropriate width on a combination slitting and rewinding machine. It is difficult to provide a chuck which firmly holds such a cardboard tube at high rotational speeds without slippage and without severely damaging the tube. The invention is directed to a novel chuck which is simple in design and, therefore, economical to build, and which is highly effective in overcoming the aforemention problems.
Briefly stated, the invention is in a chuck for engaging and holding the open end of a hollow core or tube on which a web of material is spirally wound. The chuck comprises a cylindrical flange having an integrally formed outstanding smaller diameter cylindrical hub which extends outwardly from the flange and is designed to be received in the open end of the tube. The hub and flange are provided with a plurality of L-shaped arcuately spaced slots which are radially oriented relative to the longitudinal axis of the hub. A sear is disposed in each of the slots and is specially shaped to rock therein in a radial plane relative to the longitudinal axis of the hub. Each sear is generally L-shaped and has a pair of legs which are angularly disposed to each other, the first of the pair of legs resting in the portion of the slot formed in the hub and the second of the pair of legs resting in the portion of the slot formed in the flange. Each sear is shaped so that the first leg will be free of contact with a hollow tube mounted on the chuck in surrounding relation to the hub, when the tube does not engage the second leg, and the first leg will be correspondingly moved into engagement with the inner periphery of the hollow tube surrounding the hub, as the tube engages and moves the second leg in the direction of the flange sufficiently to cause the sear to rock. Any suitable means are provided for retaining the sears in the slots during rotation of the chuck.
U.S. Pat. No. 1,882,950 shows and describes a chuck which employs differently shaped sears that are positioned in slots found only in the hub and which are designed to engage only the inner periphery of a hollow tube as it is mounted on the chuck. The sears, shown in this patent, are typically long and necessitate the use of a lengthy hub which minimizes the length and number of tubes that can be placed, for example, on a slitting and rewinding machine wherein the tubes are individually mounted between a pair of chucks which, in turn, are fastened to a pair of stubbed shafts at the free outer ends of a pair of rewind arms that are normally mounted on a common support shaft. The stubbed shafts and attached chucks, carried by each pair of rewind arms, are movable laterally to and from each other to accommodate mounting of the tubes on the machine. The amount of lateral movement of the chucks affects the length and number of tubes that can be mounted on a machine and is naturally dependent upon the shape of the sears and the corresponding length of the hubs which house the sears. It can be appreciated from the above that the number and length of the tubes are maximized by the use of short sears and hubs. This is a big advantage of the invention which is in a chuck that utilizes specially shaped sears which are compact and require minimum length hubs, but which are highly effective in preventing slippage of the tubes on the chucks at high rotational speeds.